mfd: Add STM32 LPTimer driver

STM32 Low-Power Timer hardware block can be used for:
- PWM generation
- IIO trigger (in sync with PWM)
- IIO quadrature encoder counter
PWM and IIO timer configuration are mixed in the same registers so
we need a multi fonction driver to be able to share those registers.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

1 files changed, 107 insertions, 0 deletions

diff --git a/drivers/mfd/stm32-lptimer.c b/drivers/mfd/stm32-lptimer.c
new file mode 100644
index 000000000000..075330a25f61
--- /dev/null
+++ b/drivers/mfd/stm32-lptimer.c
@@ -0,0 +1,107 @@
+/*
+ * STM32 Low-Power Timer parent driver.
+ *
+ * Copyright (C) STMicroelectronics 2017
+ *
+ * Author: Fabrice Gasnier <fabrice.gasnier@st.com>
+ *
+ * Inspired by Benjamin Gaignard's stm32-timers driver
+ *
+ * License terms:  GNU General Public License (GPL), version 2
+ */
+
+#include <linux/mfd/stm32-lptimer.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+
+#define STM32_LPTIM_MAX_REGISTER	0x3fc
+
+static const struct regmap_config stm32_lptimer_regmap_cfg = {
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = sizeof(u32),
+	.max_register = STM32_LPTIM_MAX_REGISTER,
+};
+
+static int stm32_lptimer_detect_encoder(struct stm32_lptimer *ddata)
+{
+	u32 val;
+	int ret;
+
+	/*
+	 * Quadrature encoder mode bit can only be written and read back when
+	 * Low-Power Timer supports it.
+	 */
+	ret = regmap_update_bits(ddata->regmap, STM32_LPTIM_CFGR,
+				 STM32_LPTIM_ENC, STM32_LPTIM_ENC);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(ddata->regmap, STM32_LPTIM_CFGR, &val);
+	if (ret)
+		return ret;
+
+	ret = regmap_update_bits(ddata->regmap, STM32_LPTIM_CFGR,
+				 STM32_LPTIM_ENC, 0);
+	if (ret)
+		return ret;
+
+	ddata->has_encoder = !!(val & STM32_LPTIM_ENC);
+
+	return 0;
+}
+
+static int stm32_lptimer_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct stm32_lptimer *ddata;
+	struct resource *res;
+	void __iomem *mmio;
+	int ret;
+
+	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	mmio = devm_ioremap_resource(dev, res);
+	if (IS_ERR(mmio))
+		return PTR_ERR(mmio);
+
+	ddata->regmap = devm_regmap_init_mmio_clk(dev, "mux", mmio,
+						  &stm32_lptimer_regmap_cfg);
+	if (IS_ERR(ddata->regmap))
+		return PTR_ERR(ddata->regmap);
+
+	ddata->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(ddata->clk))
+		return PTR_ERR(ddata->clk);
+
+	ret = stm32_lptimer_detect_encoder(ddata);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, ddata);
+
+	return devm_of_platform_populate(&pdev->dev);
+}
+
+static const struct of_device_id stm32_lptimer_of_match[] = {
+	{ .compatible = "st,stm32-lptimer", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stm32_lptimer_of_match);
+
+static struct platform_driver stm32_lptimer_driver = {
+	.probe = stm32_lptimer_probe,
+	.driver = {
+		.name = "stm32-lptimer",
+		.of_match_table = stm32_lptimer_of_match,
+	},
+};
+module_platform_driver(stm32_lptimer_driver);
+
+MODULE_AUTHOR("Fabrice Gasnier <fabrice.gasnier@st.com>");
+MODULE_DESCRIPTION("STMicroelectronics STM32 Low-Power Timer");
+MODULE_ALIAS("platform:stm32-lptimer");
+MODULE_LICENSE("GPL v2");